1. Field of the Invention
The present invention relates generally to avionics systems for aircraft, and more particularly to a synthetic vision system (SVS) capability for slewing the synthetic vision runway position to the observed real-world runway position when the synthetic vision runway position is observed to be misaligned.
2. Description of the Related Art
Synthetic Vision Systems (SVSs) can provide pilots with early, precise indications of runway positions, especially origin and destination runways. SVSs are database-derived applications which utilize terrain, obstacle, and runway data, precise Global Positioning System (GPS) navigation, and integrity monitoring sensors to provide unrestricted, real-time, synthetic views of the external environment regardless of weather or time-of-day. These images may be presented on, for example, a primary flight display (PFD) or multifunction display (MFD), in either a head-down display (HDD) or head-up display (HUD) configuration.
SVS runway information presented to the flight crew is typically dependent upon a solution comparison between GPS aircraft position, attitude, and an independent database containing fixed runway parameters including, for example, latitudes, longitudes, elevations, widths, lengths, and headings that describe the physical characteristics of runways around the world.
A problem exists in the case where the aircraft taxis onto the actual runway and lines up on the centerline, only to find that the SVS runway depiction is displaced from real world centerline or heading due to parameters in the runway database that vary from the real world.
U.S. Pat. Publicn. No. 20070005199, entitled “System and Method for Enhancing Computer-Generated Images of Terrain On Aircraft Displays,” by G. He, discloses a system and method for enhancing the visibility and ensuring the correctness of terrain and navigation information on aircraft displays, such as, for example, continuous, three-dimensional perspective view aircraft displays conformal to the visual environment. More specifically, an aircraft display system is disclosed that includes a processing unit, a navigation system, a database for storing high resolution terrain data, a graphics display generator, and a visual display. One or more independent, higher precision databases with localized position data, such as navigation data or position data is onboard. Also, one or more onboard vision sensor systems associated with the navigation system provides real-time spatial position data for display, and one or more data links is available to receive precision spatial position data from ground-based stations. Essentially, before terrain and navigational objects (e.g., runways) are displayed, a real-time correction and augmentation of the terrain data is performed for those regions that are relevant and/or critical to flight operations, in order to ensure that the correct terrain data is displayed with the highest possible integrity. These corrections and augmentations performed are based upon higher precision, but localized onboard data, such as navigational object data, sensor data, or up-linked data from ground stations. Whenever discrepancies exist, terrain data having a lower integrity can be corrected in real-time using data from a source having higher integrity data. A predictive data loading approach is used, which substantially reduces computational workload and thus enables the processing unit to perform such augmentation and correction operations in real-time. The '199 invention does not illustrate the use of a user input device for providing the capability of slewing the synthetic vision runway position to the observed real-world runway position when the synthetic vision runway position is observed to be misaligned, or corrected data being subsequently used to provide enhanced runway environment information for taxi operations.